In my experience it doesn't take very long on a new keyboard set or even a new layout entirely before one gets fairly up to speed. When I built my Lets Split v2 ortholinear, I put dvorak on it and getting up to speed was surprisingly fast.

The ergonomic reasons behind the lets split/ergodox make them quite worthwhile. I love my HHKB2 but a split keyboard in general feels much better for my posture.